Design Of Civil Earthquake Early Warning System Based On P-wave Detection

Starting from exploring the basic theory, as well as the domestic and foreign presentresearch situation of earthquake early warning system，designs a civil earthquake earlywarning system. The alarm principle is using the different travel time between P-wave andS-wave，quickly detect the first arriving P-wave from the background noise, and send outwarning signals before the devastating earthquake S-wave coming. The specific scheme isreal-time monitoring of construction vibration conditions, using the P-wave mainly causebuildings up and down vibration characteristics, according to certain algorithms for rapididentification of the P-wave and make a quick warning judgment.For P-wave detection mainly displays in its acceleration, according to its amplitudefrequency characteristic has carried of the detailed hardware and software programmingdesign. About the hardware circuit design, mainly comprise a signal detection circuit, microcontroller circuit, an acousto-optic alarm, liquid crystal display, wireless transceiver circuit,and so on. Three-axis accelerometer MMA7260as signal acquisition, output for X, Y, Zthree axial voltage signals.8-order elliptic filter chip MAX7400for the frequency selector,cutoff frequencies from1Hz to10KHz. High performance ADuC842microcontroller as thecontrol core. Wireless transceiver module NRF905not only expands the range of applica-tions, but also facilitates system expansion. The software program are mainly completing ofthe controller control the various peripheral circuits and data processing. In which theP-wave fast recognition algorithm is the most important. By comparing, finally selects asimple, rapid Short Term Average to Long Term Average algorithm, which principle isusing the ratio of STA and LTA to reflect the changes in signal amplitude and its growth,when the earthquake comes, the ratio will have a distinct mutation, when its value is greaterthan a certain threshold, issues an warning signal. In order to reduce the false alarm rate, thesystem has added the S-wave detection. After an alarm signal was given, immediately turnsto detect horizontal acceleration. If S-wave were detected out within a certain time, thendetermine the earthquake occurred, otherwise, automatically eliminate the alarm signal.The designed civil earthquake early warning system have high warning speed, lowfalse alarm rate, portability, scalability and other features, suitable for families, schools,factories and other places to use.